In vivo 31P magnetic resonance spectroscopy has revolutionized the study of skeletal muscle metabolism and bioenergetics. Its non-invasive nature raises it above the traditional needle biopsy technique to repeatedly assess metabolic conditions within skeletal muscle in both healthy and diseased states. Analysis of the phosphorus spectra provide a wealth of information pertinent to the metabolic capacity and state of the muscle as indicated by variables such as phosphocreatine, inorganic phosphate, adenosine triphosphate concentrations and pH. In addition to the collection of this metabolic data by the use of small surface coils, the implementation of whole-volume multi-voxel localization or 31P spectroscopic imaging provides important spatial information about metabolism in a given tissue. Prior to early 1998 the skeletal muscle researchers submitting this application had access to these powerful tools at the VA medical center in La Jolla and as the publication records illustrate were very productive. However, recently the MRI was upgraded to a new General Electric (GE) magnet and the 31P spectroscopy capability was lost. Although several of these researchers have continued to work with 31P measurements at a location 150 miles from the UCSD campus, this is a temporary and clearly sub-optimal situation. Thus, the purpose of this grant application is to restore the 31P capability to the VA Hospital MRI in La Jolla by fiinding the purchase of the LX Multi- Nuclear Spectroscopy Package manufactured by GE. This would restore the previously available and productively utilized ability to non- invasively measure indices of muscle metabolism in both health and disease allowing the planned progression of the ongoing funded research.